Research Topics

Organic Batteries

Organic electrode materials are promising candidates for next-generation batteries. They consist of widely available elements, can be synthesized using processes with a low carbon footprint, and are low in toxicity or even non-toxic. The diversity of organic synthesis reactions and molecular designs gives access to redox-active molecules and materials with tailor-made properties. Their diverse redox chemistry allows them to be used in a variety of battery cell configurations, such as all-organic anion-rocking chair batteries or metal-organic batteries using mono- or multivalent metals. They are particularly relevant for so-called post-lithium battery chemistries based on aluminium, magnesium, calcium or anionic shuttle ions.

In our research, we focus on the development of redox-active organic materials (small molecules, polymers and covalent-organic frameworks) and their evaluation, as well as understanding their mechanism of action, as electrode materials in, among others, all-organic, sodium-, aluminium- and magnesium-organic batteries.

Representative review and perspective articles:

R. Wessling, P. Penert, B. Esser*, "How Do Organic Batteries Work? Theoretical and Design Principles of Electrode Materials for All-Organic Batteries", Adv. Energy Mater. 2025. DOI: 10.1002/aenm.202500150
B. Esser*, I. H. Morhenn, M. Keis, "Phenothiazine Polymers as Versatile Electrode Materials for Next-Generation Batteries", Acc. Mater. Res. 2025, DOI: 10.1021/accountsmr.5c00053
B. Esser, H. Ehrenberg, M. Fichtner, A. Groß, J. Janek, "Post-Lithium Storage—Shaping the Future", Adv. Energy Mater. 2025, DOI: 10.1002/aenm.202402824
B. Esser, "Redox polymers as electrode-active materials for batteries," Org. Mater. 2019, 1, 63–70, DOI: 10.1055/s-0039-3401016
B. Esser, F. Dolhem, M. Becuwe, P. Poizot, A. Vlad, D. Brandell, "A perspective on organic electrode materials and technologies for next generation batteries", J. Power Sources 2020, DOI: 10.1016/j.jpowsour.2020.228814

Strained Ring Systems

Conjugated nanohoops are fascinating compounds due to their rigid shape, cyclic conjugation, and bending of their π system. We explore the effect of incorporating antiaromatic π-systems into nanohoops, of redox-active nanohoops, we synthesize and investigate chiral nanohoops, as well as more extravagant structures, such as double nanohoops. Investigations focus on the structural and optoelectronic as well as chiroptical properties of the nanohoops, their host-guest chemistry, charge-transport properties and redox activity. We explore their application as next-generation battery electrode material, and as spin filtering materials, among others.

Selected review articles by the group:

B. Esser, J. S. Wössner, M. Hermann, "Conjugated Nanohoops with Dibenzo[a,e]pentalenes as Non-alternant and Antiaromatic π-Systems," Synlett 2022, 33, 737–753. DOI: 10.1055/a-1740-7139
M. Hermann, D. Wassy, B. Esser, "Conjugated Nanohoops Incorporating Donor‐, Acceptor‐, Hetero‐ or Polycyclic Aromatics," Angew. Chem. Int. Ed. 2021, 60, 15743–15766. DOI: 10.1002/anie.202007024

Photocatalysis

We explore the use of organic dyes and redox-active compounds in photocatalysis. Our research focusses on dyes with donor-acceptor design and their use as photosensitizers in coupled catalysis, such as the hydrogen-evolution reaction (HER) or nicotinamide reduction, as well as their incorporation in so-called photosensitizer-catalyst dyads. We also established phenothiazines as redox mediators in HER, boosting turn-over numbers by enabling lower pHs and a more active catalysis.

Exemplary papers:

A. Tombrink, M. Semwal, T. Maisuradze, A. K. Mengele, D. Straub, A. Kuehne, S. Rau, S. Kupfer, B. Dietzek-Ivanšić, B. Esser, "A Donor-Acceptor Photosensitizer-catalyst Dyad for Light-Driven Nicotinamide Hydrogenation", Chem. Sci. 2026 DOI: 10.1039/D5SC08675B
D. Baumgarten, M. Gollasch, Y. Gupta, M. Jahn, A. K. Mengele, S. Rau, C. Streb, B. Esser, Working Paper, DOI: 10.26434/chemrxiv-2025-fqktb